Process for treating petroleum oil



Jime 11, 1935. c p DUBBs PROCESS FOR TREATING PETROLEUM OIL OriginalFiled July 31, 1922 Patented June 11, 1935 UNITED STATES Application.July 31, 1922, Serial No.

Renewed July11,1934

4 Claims. (C1.:196-48):

This invention relates to a process and apparatus for treating petroleumoil and refers-more particularly to a continuous cracking process inwhich the oil is converted from relatively high boiling point productsto lower boiling point oils.

Among the salient objects of the invention are to' provide a processwhereby the volume ofoil being treated remains constant while the amountof raw oil, the cracking of the oil, theamount temperature necessary tocrack it is very thin and of gasoline, and the amount of pressuredistillate can be varied. I

Thenecessity of cracking petroleum of high boiling points into lowboiling points such. as gasoline is becoming more acute owing to thedemand for gasoline rapidly increasing. In cracking high boiling pointproducts into the low boiling point products there is necessarilyproduced carbon in more or lessproportion to the amount of the highboiling point petroleum cracked.

Where the cracking of petroleum is carried on in a shell still, thecarbon produced progressively increases as the cracklng proceeds, suchcarbon being retained in the still, While the amount of oil in the stillis progressively decreased.

In the normal operation of cracking oil in a shell still the low boilingpoint products produced known as gasoline are contained in what iscommonly designated as a pressure distillate. This pressure distillateisthat distillate from the still charge which contains what is known asgasoline, kerosene, and certain additional heavier. ends. Forillustration, the pressure distillate produced contains. of gasolinedistilling between 100 and 437 F. and 50% consisting of kerosene andoils'having higher boiling points. The pressure distillate represents ofthe total oil charged into the still, and the residuum representing 40percent of the charging stock. It will be understood that thesepercentages both as to total percent distillate, its gasoline content,etc; will vary considerably from this according to the character of theoil.

In the operation of a shell still the oilis pro gressively heatedthroughout the process while maintained under the desired pressure.Therefore, the first one per cent of pressure distillate distilledoiirepresents one per cent of the total charge; the second per cent ofthe original charge distilled over represents 1.01% of the oil remainingwhile the third per cent distilled ofi of the original charge represents1.02% of the oil remaining in the still and the process is progressivein this respect, showing that the conditions are not constant, butprogressively change, and as the carbonfrom all these per centsdistilled off isaccumulated in the still and is contained in theprogressivelydecreasing amount of oil remaining in the still; it isevident that this process involves a condition that is-constantlyprogress ingftowards conditions detrimental to the continued carrying onof the process and its operation, therefore; is limited.

It is evident that the oil; maintained at the This condition applies toany apparatus whether thejexternal heat is applied to the still properor to tubes through which the oil circulates whenthe total residuum isretained in the crackingunit. It also applies to cases where additionalraw oil is fed to the cracking unit.

When attempts are made to withdraw part of the residuum from the unit itis found that the oil so withdrawn frequently contains a great- PATENTOFFICE er per cent of low boiling point products than the originalcharging stock;

One object of my invention is to overcome the foregoing objections byproviding a process whereby the volume of hydrocarbon material treatedremains constant :while the amount of raw oil fed into the system,'theamount. of pres- 35 sure distillate produced and the amount of gasolineproduced can be varied.

The single figure is a diagrammatic side elevational view of theapparatus.

The raw oil is drawn from any suitable source 40 not shown and by meansof a pump isforced through line I through valve 2, valve 3 being closed,through line 4 into the cracking coil 5. As the oil passes through thiscracking coil it from the furnace 6 through the ports I into the top,part of the chamber containing the cracking tubes and passes downwardaround the tubes to a flue not shown. The oil passing through the coilsis raised to a conversion temperature and. then passes through line 8into expansion chamber 9. t

The process is not confined to any particular kind of apparatus andwhile the oil is shown is heated by the furnace 6. The heat passes 45 asentering the side of the expansion chamber 55 mator.

near the bottom and discharges near the top as shown, it may enter atany convenient point of said expansion chamber.

The vapors from the expansion chamber pass through line lil into thebottom of the dephleg- The dephlegmator contains pans or any othersuitable arrangement for accomplishing the result which is laterdescribed. More or less of the vapors while ascending through thedephlegmator are condensed and are dropped backv ratus at which time thevalve 2 is closed and the valve Sopened and the raw oil'ied through linell into the dephlegmator through line I 8. Attention is called to thefact that this line 18 extendspart of the way down into the dephlegmatorand this is one of the essential parts of my invention which I willdescribe later. a When the apparatus is brought to the pressure. it isdesired to operate at then the surplus in .condensable gas is taken onthrough line l9, either continuously or intermittently, beingcontrolledby valve 26. This may be a hand control 'valve or an automaticallyoperated valve.

The pressure distillate flowing .into the pressure istillate tank {6 isdrawn off through line 2| controlled by valve 22 to any suitablestorage. The amount of liquid in the receiving tank l6 is ascertainedthrough a gauge glass or any other convenient means well known to theart. The raw oil, asTwillbe noted, is discharged into the ephlegm'atorat a point which will bring the vapor'sin contact with'this raw oil soas to obtain the highest efficiency of transfer of heat fromsai'dfvapor's to said raw oil feed, also allowthe superheat to'beextracted from the said vapors/by said raw oil at the earliest possiblemoment, thus causing condensation of the higher "boiling point vaporsas" quickly as possible and thereby decreasing the velocity of thevapors through the dephlegmator and overcoming the tendency 16f thesevapors to mechanically carry over "withthe remaining vapors an excessiveamount of'high boiling point ends.

"The Too'ndensed highboilin'g point vapors and the unvapdnzed portion ofthe raw oil feed contin'uou'sly pass down through dephlegmator legliflthrough line l2, through cracking coils 5, through line 8 intoexpansion chamber 9. The dephlegmator may be elevated to a sufficientheight 'toiurnish head pressure to force the 'oil'through the crackingtubes, or this oil may be "forced through the cracking tubes byinterposing a suitable force pump of well known design in'line l2.

. The expansion chamber is properly insulated so that :the amount of.heat radiated therefrom can be controlled but it is preferred toinsulate the expansion chamber in such manner that the temperature inthe same may be controlled. A portion of the oil in the form of vaporscontinuously passes through line ll! into the bottom of the'dephlegmatorand is subjected to the action of the raw oil being fed thereto with theresult as already ydescribed. The remaining vapors 'ately.

pass beyond the discharge of the raw oil for further cooling with thefurther result that more ii's'drawn out through lines 2? and 28, throughline 29, through cooler at and carried through line iii to any suitablestorage or reducing still, the

flow being regulated by valves 32 and 33. The usual practice is to useline 21 until the accumulation of carbon in the expansion chamberinterferes and then line '28 is used. Additional lines may be providedfor drawing off this oil at higher elevations on the expansion chamber.

The manhead 34 is for cleaning the carbon out of the expansion chamber,while manhead 35 is for ventilation andfor allowing a man to probe 7 thecarbon out of the retort without entering it.

By this process at least 95% of the carbon remaining in the apparatusand produced from cracking the oil will be contained in the expansionchamber and not more than 5% will-be contained in the cracking tubes 5,which is of great advantage. 7

In treating crude oil containing a certain percentage of naturalgasoline such natural gasoline contained therein will be vaporized inthe dephlegmator and drawn ofi from the system with the pressuredistillate, thusavoiding such'gasoline passing through the crackingtubes, hence will allow the cracking tubes to be used for crackingnothing but oil containing no gasoline and of course'avoidingtaking fromthe cracking tubes a part of their capacity 'by passing gasoline throughthem. V v

7 Should the crude oil being treated contain sufiicient quantity ofnatural gasoline, or other products desired as to use more heat tovaporize such gasoline or other desired productsthan is desired toextract from the vapors in the dephlegmator, then such oil may bepreheated to such temperature not in excess of that extracted fromthempors in the dephlegrnator. This method may be variedif desired, byby-passing some of the raw oil directly to the cracking coils throughline 4 by partly opening valve 2, but in doing this the capacity oi theplant is decreased proportion- Should the ,oil being treated containwater when fed vover the top such water content willbe converted intosteam in the dephlegmatorby the heat of the vapors in said dephlegmatorand such steam passes'w'ith the remainingoil vapors over into thepressure distillate tank [6 vand may'be withdrawn. Should the content ofw'at'er'be such as to take too much heat from the vapors in thedephlegmator then'the oil may be preheated in any suitable means beforebeing fed into thejdephlegmator, such preheating being sufiicien't sothat the temperature of the oil'will besuchas not to extract toomuch'heat from-the vapors-in the dephlegmator. Should it be desired,instead of preheating the oil, sufiicient of theoil-may be fed direct tocracking coils 5 by regulating the opening of valve 2 and the remainingportion-of 011 being fed directly into the dephlegmator, the oil goinginto the dephlegmatornot being in excess of amount regulated to takeonly the. desired 7 amount of heatfrom the vapors in the dephleg mator.

J This operation also applieswhen treatingan 'oil containing both waterand natural gasoline, that isfit may be'preheated to the proper-degree,orsuch portion of it 'p'assed throughyalve Z and line 4 to the crackingtubes asis found necessary as above described to keep the desiredtemperature in the dephlegmator. V f

' In the treatment of oil containing 'water if the temperature ofthe'vapor in the top of the "dephlegmator be maintained too low for thpressure held on' the apparatus, thesteam generated from this water-willbe condensed in the dephlegmatorand be' refluxed back to the crackingtubes and result in the apparatus beingwater vapor bound Forillustratiomthe boiling point ofwater is aboutf327 F when maintained at'100' lbs. Temperature; thereforeyat the top 1 of" the dcphlegmatorhQl1l1dj be maintainedfsufficiently high to prevent any 'substantialcondensation of the waterin the top of the dephlegmator. Avery importantfe'aturein the operation of this process with oils containing variousamounts of water is that there are no sudden variations of pressure.

To give an illustrative run using a gas oil made from mid-continentcrude oil and having a gravity of 33 B. at 60 F. 500 barrels per day ofthis raw charging stock is fed into the apparatus through line i,through valve 3, through line I! in the dephlegmator through line I 8.The vapors entering the bottom of the dephlegmator are approximately 790F., while the raw oil fed into said dephlegmator is approximately 70 F.The vapors condensed with the raw gas oil and returned pressuredistillate fed into the dephlegmator reach a temperature of about 700 to780 F., and pass down dephlegmator leg ll through line l2, through coils5 in which such oil is heated to about 814 F., and are dischargedthrough line 8 into expansion chamber. 200 bar rels of residuum aredrawn from expansion chamber through lines 21 and 28. The temperature ofthe vapors at the top of the dephlegmator is about 550 F. and 300barrels of pressure distillate are taken out through receiving tank l6.This pressure distillate is about 50 B. gravity at 60 F. and containsapproximately 50% of gasoline boiling point between 100 and 437 F.

For each barrel of raw material fed into the apparatus there are twobarrels of reflux condensate condensed from the vapors in thedephlegmator and refluxed back to the cracking tubes for furthertreatment with the raw oil fed into dephlegmator. Therefore, in theoperation there are substantially 500 barrels of raw oil being fed tothe apparatus per day, 300 barrels of pressure distillate and 200barrels of residuum taken therefrom per day, but there are 1,500 barrelsof combined raw oil and reflux being passed through the cracking tubesper day. Therefore, there is only 10% of the oil passed through thecracking coils which is converted to gasoline representing 30% of theraw oil being fed in. The pressure distillate produced represents of thetotal oil passed through the cracking coils and represents 60% of theraw oil being fed in a day. a

An important feature of my process isthat it is possible to vary theamount of gasoline, pressure distillate and the residuum withdrawn fromthesystem without substantially increasing or decreasing the totalcombined volume of reflux and.

raw oil passing through the cracking tubes in a day, or changing thepercentage of such total volume that is converted into gasoline. Thisisaccomplished by controlling the temperature in the dephlegmator throughthe fi'ow thereto or returned pressuredistillate. A pressure distillatejmay beproduced that'is rich in gasolin'eby re ducing J the "quantity ofraw oil' and simultane ouslyincreasingthe how of returned pressure 1distillate fed to the dephlegmator, or a larger volumepf pressuredistillate may he -produced by increasingthe ra w'oil and decreasing thereturned' pressure distillate" fed to the dephlegmator. In each instancethe temperature 'of the dephlegmator so "controlledby the 'flo'w ofreturned pressure distillate, a large percentage of which vaporizestherein, that the volume o freflux condensate' plus the' raw oil chargereturned to the heating coil" is-mai'ntaind const nt: 1 -I claim as myinven'tion: l I; A continuous process for cracking hydro? carbon oil'c'onsist'ing in passlngla constant vol ume"of combined charging oil andreflux com densfate through a heating" zone 'whereirr it' is raised to acracking temperature, in "delivering the-heated' 1 oil from 5 saidh'eat'ing" zone to a reaction zone wherein conversion occurs and from gwhich no'unvaporized oil is permitted to return to the heating zone, inpassing evolved vapors to a dephlegmating zone wherein they aresubjected to reflux condensation by passage in heat interchange relationwith the incoming charging oil, in reducing the proportion of chargingoil and increasing the proportion of reflux condensate in said constantvolume of oil introduced to the heating zone by decreasing the amount ofcharging oil introduced to the dephlegmating zone and simultaneouslyreturning to the dephlegmating zone an amount of the pressure distillateproduced by the process sulficient to compensate for the decreasedcondensing elfect due to the decrease in the amount of charging oilintroduced to the dephlegmating zone.

2. Aprocess for treating hydrocarbon oil con sisting in continuouslyintroducing a constant volume of combined raw oil and reflux condensateto a heating zone wherein the oil is subjected to cracking conditions oftemperature and pressure, in subjecting the evolved vapors to refluxcondensation in a dephlegmating zone to supply the reflux condensate insaid constant volume of oil, in introducing the charging oil to thedephlegmating zone to flow therethrough in heat interchange relationwith the vapors'and commingle with the reflux condensate, in loweringthe proportion of charging oil to reflux condensate in said constantvolume of oil by decreasing the amount of charging oil introduced tosaid dephlegmating zone and in simultaneously introducing to saiddephlegmating zone an amount of the pressure distillate produced by theprocess suflicient to compensate for the decreased condensing effect dueto the decrease in the amount of charging oil introduced to thedephlegmating zone.

3. A conversion process which comprises continuously passing a mixtureof charging oil and reflux condensate in a restricted stream through aheating zone and heating'the same therein to cracking temperature underpressure, subsequently separating the heated mixture into vapors andresidue, fractionating the vapors in a fractionating zone in contactwith fresh charging oil for the process to form said mixture for passagethrough the heating zone, finally condensing the fractionated vapors andintroducing resultant final condensate into contact with the vaporsundergoing fractionation, and, throughout the normaloperation of theprocess, so correlating the aammntmifinalrcundensate thfinals-mutingtzone with thexamountm char in oil to the tractionatinczone aste e ubstantiailly constant the yolwne cf the mixture nfycha-lyging oi1 rflild --reflux condensate which is in :theifractipnatin g zone and massed thetlaztter to the heating zone,wombined-mooling.zaction-of thet'cha lg n 011 andzfinal condensateintroduced [to the fracitionating "zone .sufimient ltqz-gmmintafm insaid mixtures uantity 10f reflux condensate lat teastftmicezthat ofthecharg ingtnil.

V the .-\crac ing of hydrocarbon .oils, "the method which comprisestrfnactionating the cracked waporstin a, iractionating zone in contactwith a, first stream of charging oil forlthe pnoc ess .tO condense:msuflicientlyfcnacked fractions thereaortas .zre'fiux condensate, thencombining :this chargingnil and the nefluxlcondensate withl'aflsec.

--ond stream 10f ,charg-ingeoiL-passing the resultant ,mimuiziegofcharging-ail and reflux condensate through a vheating mne and heatingthe -same ttheneintto creams-immat e :pmssu e, .sepamti athe ehea-tedmixture into 1mm. residue summing the iormer :150 th Imotio s ms -zone a@sa d crat cd ,m o "finally =ccnd nsing =the fract onat d "vapors windintro .duqmg a, portion. .Qf-

resultant final-c ndensat into contact with the vaporsinitheegfractionating zone, th amountm chatging' ikand finese edensate-=intt9du ced to thetiractionatiqg zone-he.-

r u ficient tgx form in ;the latter a. volume at treflux eqndensate :at:least twice :the combined volumecf said fiIStzflIldr-SGGQDdQStEQQXHS10f charging m1, :'a nd .thmughcut the enqrmal gpensticn of the processso.-corr lati11g the amount 01 final condensat introduced into t e insticnating zone with ,thetamQu nt of charging "ail imsaid first and secndstrpams asto maintainst1 8ntia y mm fistant the volume tor,saidtmixtuiielof char in 01,1 and-reflux gcondensate massed through theheating-zone.

. amour. Dumas,

